A HPLC-MS method to detect and quantify guanfacine in urine.

Area of Science:

• Pharmacology
• Analytical Chemistry
• Forensic Toxicology

Background:

• Guanfacine, an alpha2A-adrenergic agonist, is increasingly prescribed for adolescent ADHD.
• This expands its use beyond hypertension, necessitating reliable urine testing.
• Monitoring guanfacine levels is important for compliance and abuse detection.

Purpose of the Study:

• To develop and validate a simple, rapid HPLC-MS method for detecting and quantifying guanfacine in urine.
• To establish a reliable analytical tool for therapeutic drug monitoring in adolescents treated with guanfacine.

Main Methods:

• Urine samples were processed using ethyl acetate extraction with protriptyline as an internal standard.
• Analysis was performed using high-pressure liquid chromatography-mass spectrometry (HPLC-MS) on a YMC Basic column.
• Detection utilized positive electrospray ionization with selected ion monitoring, achieving elution in under 5 minutes.

Main Results:

• The method demonstrated an analytical range of 20-2000 ng/mL, with limits of detection and quantitation at 5 ng/mL and 20 ng/mL, respectively.
• High precision (<15% CV) and recovery (>89%) were achieved across tested concentrations.
• Analysis of 100 urine specimens revealed 11 positive results, indicating the method's utility in real-world scenarios.

Conclusions:

• The developed HPLC-MS method is a simple, rapid, and effective tool for routine guanfacine detection and quantification in urine.
• This assay supports clinical monitoring of guanfacine therapy in adolescents.
• The method's reliability aids in assessing patient compliance and identifying potential misuse.